Supergirl Punches [SPOILER] in New Teaser Trailer

The fifth season of Supergirl has only just begun and already, it's bringing with it plenty of questions. As the mystery of Martian Manhunter's brother intensifies, a promo for next week's episode has revealed a shocking fight scene between two characters fans never would have expected.

The teaser for "Stranger Beside Me" takes a surprising turn when sisters Kara and Alex Danvers fight in the middle of the day in National City.

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"Sibling rivalry is contagious," the trailer warns before showing Alex deflect Supergirl's heat vision blast. However, the fight becomes even more devastating when the Girl of Steel hits her adopted sister and sends her flying through the air.

For the time being, all we have are questions. Surely Kara would never willingly fight her sister, so we might be dealing with a shape-shifter, a colored Kryptonite or perhaps even mind-control. Still, whatever the case may be, the odds aren't exactly in Alex's favor.

The two sisters previously traded blows on the series, but that was done in a training room, in order to up Kara's fighting game.

RELATED: Supergirl: Martian Manhunter's Brother Just Got More Mysterious

Airing Sundays at 9 p.m. ET/PT on The CW, Supergirl stars Melissa Benoist as Kara Danvers, David Harewood as Martian Manhunter, Mehcad Brooks as Jimmy Olsen and Chyler Leigh as Alex Danvers.

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